Intestinal villi are tiny, finger-like projections that protrude from the epithelial lining of the intestinal wall. Each villus is approximately 0.5-1.6 mm (millimetres) in length and has many microvilli (singular: microvillus

Microvillus

Microvilli are microscopic cellular membrane protrusions that increase the surface area of cells, and are involved in a wide variety of functions, including absorption, secretion, cellular adhesion, and mechanotransduction....

), each of which are much smaller than a single villus. Intestinal villi should not be confused with the larger folds of mucous membrane

Mucous membrane

The mucous membranes are linings of mostly endodermal origin, covered in epithelium, which are involved in absorption and secretion. They line cavities that are exposed to the external environment and internal organs...

 in the bowel known as the plicae circulares. A villus is much smaller than a single fold of plicae circulares.

Villi increase the surface area of the intestinal wall.